Fire alarm apparatus



March 4, 1952 M. P. REECE FIRE ALARM APPARATUS l 5 Sheets-Sheet l O CU 4 Filed Nov. 18, 1948 i lHJ. -lNiHU. A L A m m m A m :NNIiwIVL V -L H A H M. P. REECE FIRE ALARM APPARATUS March 4, 1952 5 Sheets-Sheet 2 Filed NOV. 18, 1948 N @i N @i MMU- 1 1, If d 2 w nl@ 2 H EN# l i m L?? Q w- 1-2m u mv m m n T m N m a m m m r rn Lm .n -L P L JVU ,w U1: 2m@ h@ @hw ,E A 1 04mm O| @Zr-.4m5- OJ 04mm O| @Zr-.JNE O| mi.. -Ulli 1 Il. .i- ...HJ u m gi, Ql

March 4, 1952 I M, P, REECE 2,587,762

FIRE ALARM APPARATUS Filed NOV. 18, 1948 5 Sheets-Sheet 3 Patented Mar. 4, 1952 UNITED STATES PATENT OFFICE 2,587,762 FIRE ALARM APPARATUS Michael P. Reece, London, England, assignor, by mesne assignments, to Pyroban Developments Limited, Manchester, England,` a'body corpo- Q rate ofl Great Britain Application November 18, 1.948, Seri-al N o. 60,790V In Great Britain November 25, 1947 z claims. (c1. 177-355) temperature of the surrounding air causes the apparatus to operate.

According to the invention a pair of resistor elements are connected in series with the coil of a polarized relay, a predetermined rate of temperature rise in the ambient temperature of the air upsetting the balance of the polarized relay to operate an alarm signal.

A further feature Vof the invention is the provision of a further coil in the main circuit capable of operating indicating mechanism for fault location.

The invention will be described with reference to the accompanying drawings:

Fig. l is a circuit diagram showing one embodiment of the invention;

Fig..2 is a circuit diagram showing a modified embodiment;

Fig. 2a, shows a modied detail modication of Fig. 2;

Fig. 3 is a side elevation, partly in section, at an enlarged scale of a detector head shown in Figs. l and 2;

Fig. 4 is a side elevation partly in section of same at right angles to Fig. 3; and e Fig. 5 is a plan of same. l

The apparatus4 comprises one or' more detector heads I connected in series where more than one is employed. Each detector head I comprises two resistor elements a, d (see also Figs. 3 and 4) one element a being wound on a skeleton former 2 more fully to be described presently with adjacent turns separated so as to present a large surface area in relation to its weight. The second element d is wound on the same former, with its varnished turns close together and overlapping so as to provide a small surface area in relation to its weight.. The former 2 comprises a base plate 3 having four fabric covered rods 4 around which the elements a and'd are wound. The

` turns of the second element d may be lagged with other endY of the Spring@ .isarrisd by@ Pillar A resistance strip cmay be con- 'I mounted on the base plate 3. The former 2 is suspended from a ceiling or in any other suitable position so that air may circulate freely around the elements. The base plate and terminals are enclosed in a cover 8 carried by a spindle 9 secured to the former 2, the cover leaving a clearance space between the ceiling or other surface and the base of the cover so as to allow the circulation of air over the winding of the elementa.

`The two elements a and d are connected in parallel across a D. C. supply 9| through a polarized relay 5I and a potentiometer R1. One end of each element a and d is connected in series with a coil e or coil f, respectively, of the polarized relay 5I, the two coils e and ,f of which are wound in opposition, the free ends of the coils e and f being connected by the potentiometer R1, the movable contact R of which is fed from one terminal of the D. C. supply 9| through the main circuit. The D. C. supply may be obtained from la battery or through a rectiiier from A. C. mains.

The polarized relay 5I is adjusted by moving the contact R" and the potentiometer R1 so that at normal temperatures the currents passing through the coils e and f are equal and balance each other, and no resultant magnetism is available which could operate in the manner more fully described hereinafter a relay circuit 'II containing an alarm device such as a red lamp 6I vand/or an audible alarm bell or gong 8|. Howlever, if the temperature rises, the resistance in the main circuit will vary and the relay circuit Will be operated.

The warning circuit is operated by a reed II suspended between the coils e and f, the free end lof the reed normally resting between two contacts h and g, the contact g being connected to the lead 6I' to the lamp 6I. The reed II makes contact with the contact g if any current being out of balance should circulate in the coil f. The relay circuit II comprises a coil I2 and two pairs of contacts I3 and I4. When the reed II makes Contact with the contact g the coil I2 is energised so as to close the contacts I3 and I4, the closing of the contacts I3 operating the alarm device 8|.

The second pair of contacts I4 a're connected in a resetting circuit in series with a variable resistance R2 across the coil f and part of the potentiometer R1. The closing of the contacts I 4' reduces the current flowing in the compensating winding f of the polarized relay 5I and causes the ,reed II to leave the contact g thereby resetting .the circuit.

1f the disturbing conditions i. e. the increase flows in each of the parallel windings a and d. through the detector head I and through coils e and f of the polarized relay, the ratio of the two currents being adjustable by means of the potentiometer R1. When any outof. balance. current flows in either coil e or f due tochange .inthel resistance of either winding a or d due tochange in temperature the reed II is operated to make contact with the. contact g to operate the alarm device.

An out of b alance current can' be caused also with a slow rise of temperature which acts substantially at the same rate on both windings a and d by firing the strip of low melting anchor ingbead 6 of the spring b so that the short-circuit 'of` the'strip c is removed and the windings a and d carry diierent currentsV thereby unbalancing Vthe circuit andcausing the operation of the alarm devices.

The'arrangement shown in Fig. 2 is applicable for' industrial purposes such as for use in coal mines', on aircraft, or other applications.- The main circuit is similar to that hereinbefore described, but includes a fault relay I5. The potentiometer R1 may be replaced by a potentiometer R3 in series with the coil f (Fig. 2a) and has a tapping point in series with the relay I5 which providesv a somewhat finer adjustment.

The coil of the relay I5 is of low resistance and the current normally iiowing in themain circuit is arranged so as to hold contacts IIiY closed. Should the current fall below a predetermined value therelay'contacts IE open and contactsv I1 close. The closing of contacts I1 illuminates-a lamp I3 which may be coloured amber'and indieating a circuit fault. Simultaneously ay relay coilIBis energised to close contacts and'sound a faultindicating buzzer 2l. Thus if any of the leads to the head I arey severedor'the heads I themselves are damaged the current owing in the main circuit will fall in value andthe fault ndingcircuit will give an indication thereof. A similar operation of the relay I9' occurs if the supply of current to the mainfcircuit drops. For use in mines plate rectiers vmay be arranged -in parallel with the coils so as to reduce sparking.

The opening of the contactsv I6 of the relay-I5 also vopens the circuitof the reed I IY of the polarized relay 5I thereby preventing a spurious operation of the lire alarm device.

Where a number of units each comprising one or more heads are employed the position-of the relay I9 and the lamp I8 may be reversed so that each vunit is provided with a lamp IB' operated in parallel from a single relay I5 which'will cause the lamp in the faulty circuit to be illuminated and also operate the buzzer 2|.

In order to indicate normally that the circuit is operating the reed II rests in contact'with'the contact .h in series with a lamp 22which may be coloured green.

A push button switch 22|V may be providedin order to prevent thecircuit from being; reset automatically so that the circuit' remaiIIsin'its 4 alarm condition until reset manually by operation of the switch 22I.

A test circuit may be incorporated by introducing a single pole two way switch 23 which normally completes the circuit between the rheostatfR'andpoint 24 butwhich;v when loperated connectsY the'- potentiometer B2i to a point 25 thereby putting the potentiometer R2 in shunt with the winding e thus reducing the current flowing-therein and simulating a disturbing condition at the heads I.

In: cases where: relatively high temperatures arenormal suclras in aircraft engines the detector. heads may be constructed on ceramic formersand' the elements a and d may consist of tungsten wirefsonasfto only operate when a predetermined'. temperature has been exceeded.

Four, heads I are shown in series in the drawings but one or two or up to twelve or more may be employed.

I claim:

1. A fire alarmy apparatus comprising in: combination a current source; ar detector head;A a

iirst resistor element and a second resistor element arranged. in saidvhead and each connected with-one end thereof to a terminalof saidcur-r rent source; a polarizedA relay having a. rst coil and asecond coil wound in opposition. to said first coil, said iirstu coil being connectedY in series with said first resistor element and said second coil being 4connectedin series with said second resistor element; a potentiometer con.- necting said rst.coil.,and said second coil with each other so as to provide a balancedcircuit at normal temperatures; a;A reed arranged between said coilsof' saidpolarized relay for de.- fiection out of f itsnormalposition. by any. outof-baiance currents flowing.. in. saidy polarized relay; a contactarranged at: the free endof said reed; a secondary circuit energizedibythe closingv of said contact! offsaidreedso. as to be closed when an out-of-balance current. ows in said-polarizedirelay; afrst relayin said secondary circuit, saidV1 i'sti'relay' being-energized when an out-of-balance current 'ows' in said polarized: relay; a-pair'ofcontacts operated by said relay so asf--to'lbei closedzuponthe venergization thereof; a warning deviceonnected in series to said pairfoficontacts-so las--to be operatedwhen an out-of-balance. current..flows; insaidpolarized relay; a secondzrelay; connectedl to said current source; arstpairrf-of contacts operated'by said secondzrelay andiconnected inV series to. said reed, saidzrstipairof.contacts opening when vthe current through saidsecond-relay falls ,below apredetermined vaiue andrthusfinterrupting said secondary cirouit2.in .order' to. prevent a spurious opera-tionof; said.warning. device.; a second pair ofl contactspperatedby said second relay, said second pair of. contacts.. closing whenv the currentxfthrough said, second. relayfalls, below the predeterminedvalue; anda fault-indicating cevice connectedQto. said. second pair of contacts so .as .tobe operated bythe closing thereof simultaneously withthe opening of said first pair of contacts of said second relay.

viirst coil, saidrst coil Abeing connected; in series with saidy first resistor-- element andsaid secassmec ond coil being connected in series with said second resistor element; a potentiometer connecting said rst coil and said second coil with each other so as to provide a balanced circuit at normal temperatures; a reed arranged between said coils of said polarized relay for deflection out of its normal position by any out-of-balance currents flowing in said polarized relay; a contact arranged at the free end of said reed so as to be closed when an out-of-balance current ows in said polarized relay; a secondary circuit energized by the closing of said contact of said reed; a first relay in said secondary circuit, said rst relay being energized when an out-of-balance current flows in said polarized relay; a pair of contacts operated by said relay so as to be closed upon the energization thereof; a warning device connected in series to said pair of contacts so as to be operated when an out-of-balance currentI flows in said polarized relay; a second relay connected to said current source; a rst pair of contacts operated by said second relay and connected in series to said reed, said rst pair of contacts opening when the current through said second relay falls below a predetermined value and thus interrupting said secondary circuit in order to prevent a spurious operation of said warning device; a second pair of contacts operated by said second relay, said second pair of contacts closing when the current through said second relay falls below the predetermined value; a fault-indicating device corineoted to said second pair of contacts so as to be operated by the closing thereof simultaneously with the opening of said rst pair of contacts of said second relay; a rheostat; and a single pole two Way switch for connecting one of said coils of said polarized relay in shunt With said rheostat in order to reduce the current in said coil thereby simulating a disturbing condition at said detector head.

MICHAEL P. REECE.

REFERENCES CITED The following references are of record in the i'lle of this patent:

UNITED STATES PATENTS Number Name Date 245,272 Bright Aug. 9, 1881 419,710 Robbins Jan. 21, 1890 1,954,832 Ruben Apr. 17, 1934 2,000,074 Grant May 7, 1935 2,003,358 Grant June 4, 1935 2,003,443 Henneberger June 4, 1935 2,219,262 Mample Oct. 2, 1940 2,236,891 Bridges Apr. 1, 1941 2,302,593 Bean et al Nov. 17, 1942 2,398,892 Kelly Apr. 23, 1946 2,412,471 Olson Dec. 10, 1946 2,448,575 Burdick Sept. 7, 1948 

